Field of Invention
The present invention relates to an electrical contact material, and is especially a preparation method of an electrical contact material.
Description of Related Arts
Silver based electrical contact is core element of electric switch, taking charge of connecting and disconnecting between circuits and widely used in low-voltage apparatuses, such as various air switches, relay, ac/dc contactor, etc. In recent years, with the continuous improvement of industrial application level and cost-performance demand, new preparation technologies and silver based electrical contact composite materials have been being launched constantly.
Through searching the existing technologies, there is a new electrical contact material preparation method disclosed by 2011 declared authorized Chinese patent (201010579827.4, the preparation method of particle orientation arrangement reinforced silver based electrical contact material). Firstly, prepare Ag-coated enforced particle's intermediate composite particle with chemical plating coating method. Secondly, further mix intermediate composite particles with pure silver powder to reduce reinforcement content to finished product level. Thirdly, conduct powder-mixing, pressing, sintering and hot-extruding, etc. Finally, obtain a new electrical contact material, where the enforced particles in the matrix present fibrous arrangement.
The conventional powder metallurgy technologies usually perform one-time mixing of reinforcement powder and silver powder. Due to reinforcement powder particle size distribution, a considerable proportion of ultrafine reinforcement powder excessively disperse in silver matrix, thus lower the electrical contact material's electric conductivity and elongation. Above technical principle means to restrain fibrous arrangement form of enforced particles in local region, as such form harmfully affect material electrical property and mechanical property, thus improve the material electric conductivity and elongation. The silver in such local region only plays the role of reinforcement carrier, while the contribution of precious metal silver therein to the integral material's electric conductivity and elongation is limited.
Through further literature search, the main inventor of above invention patent published a research article entitled “Ag/(SnO2)12 Electrical Contact Material with Fibre-like Arrangement of Reinforcing Nanoparticles: Preparation, Formation Mechanism, and Properties” on 26th International Conference on Electrical Contact (ICEC2012) in May 2012. This article introduced the preparation method and material property based on similar theory. The specific description as follows: firstly, utilize mechanical alloying to prepare Ag/(SnO2) intermediate composite particles with 60% SnO2. Secondly, mix Ag/(SnO2) intermediate composite particles and pure silver powder by 1:4 to reduce SnO2 to 12%. Thirdly, conduct subsequent techniques such as pressing, sintering and hot-extruding, etc. Finally, obtain the new Ag/(SnO2) environmental electrical contact material, where SnO2 in the silver matrix present fibrous arrangement. Compared with the conventional powder metallurgy technology, the electrical resistivity reduces from 2.31 μΩ·cm to 2.08 μΩ·cm, and the elongation increases from 7% to 24%.